The most valuable stamp in the world is an ugly, faded morsel with clipped edges. It's the color of a rose petal. The one-cent magenta was issued for a penny in 1856 in British Guiana, a colonial outpost in South America and bought at auction in 2014 for $9.5 million.

"To some collectors, the one-cent magenta is the Mona Lisa of stamps," New York Times reporter James Barron writes, "but its face has no face, just a workmanlike image of a schooner and a Latin motto that is usually translate